<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    body {
        background: url(images/10.png) no-repeat top center/cover;
    }
</style>

<body>
    <script>
        const random = Math.floor(Math.random() * 10) + 1
        // const body = document.querySelector('body')
        document.body.style.backgroundImage = `url(images/${random}.png)`
    </script>
</body>

</html>